Some laptops (I've seen it on a lot of Thinkpads) include a physical cover that can be slid over the webcam when you aren't using it. While that doesn't cut power to the camera or mic, I figure would pretty straightforward for manufacturers to add contacts to the camera cover to use it as a power killswitch instead of just a privacy cover.

I think that's pretty standard outside the Apple ecosystem. HP seem to have this on most (if not all) the laptops I've seen at $DAY_JOB which uses HP for all laptops.